Re: Flat Coil Concept

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Mddeming-at-aol-dot-com>

In a message dated 3/8/02 8:23:35 PM Eastern Standard Time, tesla-at-pupman-dot-com
writes:


>
> ??  Also, Is there really any
> special frequency that tesla coils operate best at or
> is it just that 200khz is a nice frequency to transfer
> energy to the secondary???
>
> thanks
>
> Cory Roussel
> G1 Geek# 1206  
>
>



Hi Cory,
         In an ideal Tesla coil system, it is necessary that L1C1=L2C2. Because
f=1/(2pi*sqrt(LC)) frequencies much above 300 KHz or much below 100KHz require
components that are inconveniently large or  inconveniently small. If the
primary cap (C1) is too small, it doesn't store much energy and the primary
coil (L1) becomes unwieldy. Too small a primary coil results in larger power
losses in the gap, and needs a capacitor that requires too much power to charge
it up in a reasonable length of time. A manageable size secondary has a certain
inductance (L2) which must balance with a reasonable sized topload
(Cself+Ctop=C2).
         Since, for a standard secondary, L=(rN)^2/(9r+10h), where r is the
radius, N is the number of turns, and h is the height,  and for a spiral coil,
L=(RN)^2/(8R+11B), where R is the average radius and B is the width (r inner-r
outer) putting in reasonable sized numbers results in frequencies close to this
range. 
         It is also very nice if your coil puts out most of its energy below
the commercial AM radio frequencies (~540KHz-1600KHz) and especially staying
away from 455KHz. Play some what-if games with the tesla design programs, or
even with the simple equations above (ie do the math) and you'll see why most
coils are in this range.

Matt D.
G3-1085